1. Field of the Invention
The present invention relates to a radio wave timepiece having a fourth wheel & pinion receive pin as an essential constituent element of a hand attaching structure.
2. Description of the Prior Art
In a portable electronic timepiece of a background art, according to a movement using a train wheel bridge of a plastic member, when a second hand is attached thereto, a metal plate is brought into contact with a lower side of a fourth stem to thereby prevent a fourth wheel & pinion from being buckled by the train wheel bridge by attaching the hand. Further, when in view of a structure of the movement, a part having a height higher than the train wheel bridge is present and the fourth stem cannot be received, there is adopted a structure of providing a metal part such as a fourth wheel & pinion receive pin made of a metal at the lower portion of the fourth stem. For example, JP-A-2001-162333 discloses a portable electronic timepiece attaching a fourth wheel & pinion receive pin made of a metal to a battery frame by providing a certain distance from a fourth stem of the fourth wheel & pinion. A load in attaching a hand is applied to the fourth wheel & pinion and is transmitted to a train wheel bridge of a plastic member of the movement. Up to a constant load, a fourth wheel & pinion support portion of the train wheel bridge is elastically deformed, the fourth stem gradually approaches a receive face of the fourth wheel & pinion receive pin, and when the fourth stem reaches the receive face of the fourth wheel & pinion receive pin, the fourth wheel & pinion receive pin receives the load. The load applied from a flanged receive portion of the fourth wheel & pinion receive pin to a battery frame is applied to a case back push up projection of the battery frame and a base receive portion of the fourth wheel & pinion receive pin and is applied uniformly to a base on which the movement is placed. Thereby, respective hands of an hour hand, a minute hand and the second hand can be attached in a state of the movement.
Meanwhile in a portable electronic timepiece with an antenna constituted by newly arranging an antenna part to a movement of a background art, a so-to-speak portable radio wave timepiece has been developed, the antenna part is the largest in parts constituting the movement and therefore, with regard to a hand pushing structure, a problem described below is posed.
That is, as shown by a plane view of a back side of a movement of FIG. 4 and a sectional view directing the back side of the movement downward of FIG. 5, the portable radio wave timepiece having the fourth wheel & pinion receive pin made of a metal disclosed in JP-A-2000-162333 is constituted by a main plate 4 in a circular shape formed with six pieces of push up projections at an outer peripheral portion thereof, a circuit board 6 attached to the main plate 4, a train wheel held by a train wheel bridge 5 of a plastic member, an antenna 8 contained in an antenna containing recess portion 4a of the main plate 4, a battery frame 20 containing a battery 10, and a metal pin 12 attached to the battery frame 20. The metal pin 12 is a part functioning as a fourth wheel & pinion receive pin made of a metal.
The antenna containing recess portion 4a is formed in a shape of a circular arc over substantially near to a half periphery on an inner side of the outer peripheral portion of the main plate 4 formed with the push up projections 9. A position of forming the antenna containing recess portion 4a is disposed on a side opposed to the containing recess portion of the battery 10 relative to a center of the main plate 4 in the circular shape. The antenna 8 contained in the antenna containing recess portion 4a is constituted by winding a wire around an antenna core 8a in a shape of a circular arc having a section substantially in a square shape.
The battery frame 20 is a plastic plate member having substantially a triangular shape substantially covering a half of the main plate 4 in the circular shape. A right side thereof is a region formed with the antenna containing recess portion, and a left side thereof is a region having a circular arc proximate to the antenna containing recess portion 4a. The battery frame 20 arranged by being partially brought into contact with a back face of the circuit board 6. Therefore, the train wheel bridge 5 of the plastic member is arranged between the main plate 4 and the battery frame 20 by interposing the circuit board 6.
The antenna 8 is a large part having a section almost reaching the back side of the movement from a top side thereof. Therefore, a back face side of the antenna 8 is projected from a back face of the circuit board 6. An amount of projecting the antenna 8 from the back face of the circuit board 6 is about three times as much as a thickness of the circuit board 6.
The metal pin 12 is a flanged metal pin formed with a flange at one end thereof. Further, the battery frame 20 is formed with a stepped through hole 13 to be inserted with the metal pin 12 from an upper side. Other end of the metal pin 12 is projected from the back face of the battery frame 20. An amount of projecting the metal pin 12 from the back face of the metal pin 12 is about a half of a thickness of the battery frame 20.
The push up projections 9 formed integrally with the main plate 4 are arranged substantially symmetrically in a left and right direction by three pieces on a right side and three pieces on a left side at the outer peripheral portion of the main plate 4 in the circular shape at intervals thereamong. Each push up projection 9 is a projection in a shape of a small circular cylinder having a front end portion in a conical shape. An amount of projecting the push up projection 9 from the back face of the battery frame 20 and therefore, an amount of projecting the push up projection 9 from the back face of the movement is made to be slightly larger than the amount of projecting the metal pin 12 from the back face of the battery frame 20. In sum, a front end of the push up projection 9 is projected more than the back face side of the antenna and more than the front end of the metal pin 12.
In the above-described movement, an attaching operation of attaching an hour hand 16 to a front end of an hour wheel, attaching a minute hand 15 to a front end of a support shaft of a center wheel & pinion in a shape of a cylinder and attaching a second hand 14 to a front end of a support shaft of a fourth wheel & pinion, respectively, is carried out by an assembling operator by using a metal plate 17 for attaching the hands placed on an operation base. That is, as shown by FIG. 5, the movement assembled up to a state immediately before attaching the time-indicating hands is mounted on the metal plate 17. Then, the front end portions of the push up projections 9 formed at the outer peripheral portion of the main plate 4 in the circular shape at substantially equal angular intervals are put into predetermined shallow mount holes formed at a surface of the hand attaching metal plate 17. At the same time, the front end of the metal pin 12 arranged at the stepped through hole 13 of the battery frame 20 is brought into contact with the surface of the hand attaching metal plate 17. Thereby, the assembling operator can carry out the operation of attaching the hands of the radio wave timepiece without buckling or destructing the train wheel bridge 5 of the plastic member and therefore, without destructing the antenna 8.
Next, FIG. 6 shows a hand attaching structure in which a case back 3 of an exterior of the radio wave timepiece is made to serve also as the above-described metal plate. In FIG. 6, constitutions of the antenna 8 and the movement are the same as those shown in FIG. 4 and FIG. 5, mentioned above. Owing to such a structure, the assembling operator can carry out the operation of attaching the hands of the radio wave timepiece without buckling or destructing the train wheel bridge of the plastic member and therefore, without destructing the antenna.
However, according to the above-described hand attaching structure of the background art, that is, the hand attaching structure in which the fourth wheel & pinion receive pin made of the metal is provided at the battery frame of the plastic member and the plurality of push up projections are provided at the outer peripheral portion of the main plate in the circular shape substantially at equal angular intervals, there poses a problem that a planar size becomes large. Because an extra space for providing the plurality of push up projections substantially at equal angular intervals is needed at the outer peripheral portion of the main plate in the circular shape. Conversely, when the planar size of the radio wave timepiece is not made to be large, a size of the antenna cannot be made to be large and therefore, there poses a problem that a necessary receiving sensitivity cannot be ensured.
Further, although according to the radio wave timepiece having the above-described hand attaching structure of the background art in which the fourth wheel & pinion receive pin made of the metal is provided at the battery frame of the plastic member and the plurality of push up projections are provided at the outer peripheral portion of the main plate in the circular shape substantially at equal angular intervals, the battery frame of the plastic member substantially in the triangular shape covering the half of the main plate in the circular shape is adopted, an outer edge of the region on a side opposed to the region formed with the battery containing recess portion is proximate to the antenna containing recess portion. Therefore, the antenna is exposed on the back face side of the movement. Therefore, there also poses problem that the assembling operator is erroneously brought into contact with the antenna.
It is a problem to be resolved by the invention to make a planar size of a radio wave timepiece small and prevent an antenna from being exposed from an antenna containing recess portion in the radio wave timepiece having a fourth wheel & pinion receive pin made of a metal as an essential constituent element of a hand attaching structure.